Method of constructing storage tanks



May 16, 1967 H. K. KNUTSEN ETAL 3,319,32

METHOD OF CONSTRUCTING STORAGE TANKS 3 Sheets-Sheet l Filed Dec. 5l, 1965 May 16,' 1967 H. K. KNUTSEN ETAL METHOD OF CONSTRUCTING STORAGE rVANI/(S 3 Sheets-Sheet 5 May l5, 1967 H. K. KNUTSEN ETAL METHOD OF CONSTRUCTING STORAGE TANKS Filed Dec. 5l, 1963 United States Patent O 3,319,329 METHOD F CONSTRUCTING STORAGE TANKS Herbert K. Knutsen, Chicago, Ill., and Mark D. Kinghorn, Schererville, Ind., assignors to Union Tank Car Co., Chicago, Ill., a corporation of New Jersey Filed Dec. 31, 1963, Ser. No. 334,784 10 Claims. (Cl. 29--428) This invention relates in general to floating roof storage tanks. It deals more particularly with a method of constructing a floating roof storage tank.

It is an object of the present invention to pr'ovide a new and improved method of constructing a oating roof storage tank.

It is another object to provide a new and improved method of elevating the roof in a floating roof storage tank.

It is still another object to provide a meth-od of pneumatically elevating the roof in a oating roof storageA The foregoing and other objects are realized in accordance with the. present invention by providing a method of elevating a storage tank roof on a cushion of air o r the like and assuringthat the roof remains level throughout the elevation operation. The method contemplates utilizing a predetermined number and precisely positioned arrangement of support posts around the peripheryof the tank roof, extending through guide sleeves in thefroof.,

The upper end of each of these properly positioned' posts (or an extension thereof) is connected to the roof adjacent a corresponding sleeve by an adjustable tension device and the roof is continually leveled as it moves up-A wardly on the cushion of air introduced under pressure beneath the roof. A sealing arrangement prevents excessive air losses from beneath the roof as it is raised onV its pneumatic cushion. v

Once raised, the roof is supportedon the aforementioned posts and a plurality of -other posts, identicaluin construction and subsequently mounted in similar sleeves extending through the roof. Air pressure is released from under the roof and construction personnel may enter to accomplish necessary finishing jobs beneath the roof.

In the invention, both as to its organization and method of operation, taken with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIGURE l is a perspective view of a 'oating roof storage tank in operation, with parts broken away; e

FIGURE 2 is an enlarged sectional view through onehalf of the tank seen in FIGURE l, with the tank roof illustrated in various positions;

FIGURE 3 is a further enlarged sectional view, broadly' similar to FIGURE 2, with the tank roof raised according to the present invention to facilitate work thereunder;

FIGURE 4 is a further enlarged sectional view of a portion of the tank roof illustrating a sleeve mounting;

FIGURE 5 is a sectional view taken along line 5-5 of FIGURE 3; and

FIGURE' is an enlarged sectional view of an alternate 3,319,329 Patented May 16, l1967' lCC seal arrangement utilized in the method embodying features of the present invention.

roof 11 on an elaborate and extensive scaffolding withinA I of the roof 1-1, of course.

Since the tank 10 is circular in plan, the roof 11' corresponds in shape. The diameter of the roof 11 is slightly less than the diameter of the cylindrical wall 15 of the tank 10, of course, leaving an annular space 16 between the peripheral wall 17 of the roof 11 and the wall 15. This space 16, which averages out to about six inches in width, contains a sealing arrangement 18 mounted on the peripheral wall 17 of the roof 11 between the roof and the tank wall 15. When utilizing the method embodying features of the present invention, the sealing arrangement 18 is preferably of the foam seal type, similar to that illustrated in the co-pending Bodley application, entitled, Seal, Ser. No. 334,752, filed Dec. 3l, 1963, and assigned to the same assignee as the present invention. The'basis for such preference will hereinafter be discussed in detail.

The present invention is concerned with a method of elevating the roof 11 within the tank wall 15 from the position illustrated in solid lines in FIGURE 2, wherein the tank roof is resting on the bottom 20 of the tank 10,

to the elevated position A illustrated in dotted lines in FIGURE'Z. Only with the tank roof 11- raised oil 'the bottom 20 loffthe tank can necessary nal work beneath the roof 1'1, including work on the underside 21 thereof, be carriediout.M

There 'are' presently "several well-known methods of placing a tank roof 11 in the aforementionedelevated position` Asothat necessary work vbeneath the roof can be carried out. One such method is to actually construct the the 'tank shell 15. This is an expensive and time-consurning operation, however.

In contrast, f other' methods involve construction of the tank roof 11 substantially on the bottom 20 of the tank 10 and subsequently elevating it to a suitable position for completing the aforementioned work beneath theroof. Various methods of jacking the roof 11 have been employed, as-well as variousl techniques of raising-the roof .on va cushion of lluid. The present method utilizes'a 'cushion of air and eliminates the necessity for building Vsuch extensive scaffolding. Furthermore, it iscludes the series of pontoon sections 27 welded togetherin annular rings. The roof 11 here includes lan inner ring 28, an outer ring 29, and a pair of intermediate rings 30 of pontoon sections v2.7. v

The outermost wall of the outer ring 29 of pontoon sections 27 define the aforementioned peripheral wall 17 Once the roof 11 has been assembled, the seal arrangement 18 is mounted on its peripheral wall 417 in the manner described in detail in the aforementioned Bodley application entitled, Seal.

The tank 10 is normally cylindrical in shape.

A relatively air-tight seal is thus yprovided between the peripheral wall 17 of the roof 11 and the wall 15 of the tank 10.

It should probably be pointed out here that although the roof 11 is a double deck type roof, the lmethod embodying features of the present invention is advantageously used with other types of roofs as well. For example, it might Ibe utilized with a pan type-roof or a pontoon-type roof. Where the bottom 20` of the tank is crowned, either inwardly or outwardly, (as illustrated in the tank for drainage purposes, the stiffness of the double deckrtype r-oof normally necessitates providing leveling footings 25 underneath it for support Iduring construction.

According to the present invention, after the roof 11 has been assembled on the bottom of the tank 10, it is elevated .to a height satisfactory for performing the aforementioned nishing operations beneath the roof. Such work ordinarily includes vacuum testing of the plate seams in the pontoon sections 27, for example, and attachment of various drain accessories (not shown). IIn addition, certain tack welding operations between the pontoon sections 27 are ordinarily required. The footings are also removed, -of course. Furthermore, as will hereinafter be pointed out, certain types of means might be set up at this time for providing a lower roof travel limit stop for the floating roof 11 during operation of the tank 10.

According to the present invention, the roof 11 is ele.

vated to an appropriate height for performing the aforedescribed work without damaging the roof or the tank wall 15, or, for that matter, the seal arrangement '18. Furthermore, the room 11 is elevated simply .and expeditiously at a relatively low cost. In addition, the possibility of accidents and injury to construction personnel or the like is virtually eliminated.

Turning now to details of the method embodying features -of the present invention, assume that the roof 11 has been assembled on the bottom 20 of the ltank 10. At this point, a plurality of vertically disposed passages 31 are formed in the room 11 by suitable cutting techniques. In the alternative, the passages 31 might be fabricated into Ithe pontoon sections 27, of course. These passages 31 are arranged in a plurality of concentric rings and there might be a large plurality of these rings of passages; several in each ring 28, 29 and 30 of pontoon section 27, in fact. Only three of such rings '32, 33, and 34 of passages y31 are illustrated here, however, one in each pontoon section ring.

Each of the passages 31 receives a sleeve 36, and each sleeve is secured in a corresponding passage 31 by welding or the like. An upper anchor -plate 37 is welded to both the corresponding sleeve 36 and the upper deck 38 of a corresponding pontoon section 27. At the same time a lower anchor plate 39 is welded to both the corresponding sleeve 36 and 4the lower deck 40 through appropriate access ports (not shown) in the upper deck 38. It will be recognized that there are hundreds of these sleeves `36. Prior to seating the sleeves 36 in corresponding passages 31, however, a wooden plug 41 of appropriate size is inserted in the lower end 42 of each sleeve to act as `a seal `against lthe indiscriminate escape on the air under pressure utilized Ito raise the roof 11 according to the present invention (see FIGURE 4). In lieu of a wooden plug, of course, it should be understood that other plug material such as r-ags or the like might be utilized.

With all of the sleeves 36 mounted in the aforedescribed manner, three support posts 45, 46, and 47 are dropped into three predetermined sleeves, indicated at 50, 51, and 52, in the outer ring 32 of passages 31. These sleeves 50-52 are spaced 120 apart around the aforementioned outer ring I32 (as seen in FIGURE l). The posts 45-47 are pipe sections approximately ten feet long and of a diameter only slightly less than the inte-rnal diam 4 eter of the sleeve 36. When the posts 45-47 are dropped through the sleeves 50-52, they force corresponding plugs 40 out of the lower ends 41 of the sleeves. The lower ends 53 of the posts 45-47 come to rest on prepositioned base plates 54 on the bottom 20 of the tank 10.

With the lthree posts 45-47 arranged in the foregoing manner, an Iadjustable tension device 55 is mounted between the upper end 56 of each post and the upper deck 38 of the roof y11 immediately adjacent a corresponding sleeve 36, as at 57, for example. Each of these tension devices ,is substantially identical in construction and, accordingly, only Ione will be described here.

Each tension device 55 com-prises a ca'ble 60 secured to a ring 59 on the upper end 56 of the posts 45-47; the cable depending therefrom. Another cable 61 is secured to the upper deck 38 through the medium of an eye hook 62 or the like. The free end of the lower cable has a clutch unit 64 secured to it only a short distance from the deck 38, and the upper cable 60 passes through the clutch unit 64 in a well known manner. Such an arrangement is conventional and is often referred to as a chain hoist. Whether it employs cables or chains is unimportant, of course. 'In the present instance it is a five ton capacity hoist.

By manipulating the lever 65 of the clutch unit 64, the upper cable `60 is taken up to shorten the total cable 60, 61 length between the ring 59 atop Ia corresponding post -45-47, and a corresponding eye hook 62 on the deck 38. The signicance of maintaining the cable `60-61 taut or relatively taut will hereinafter be discussed in detail.

With an adjustable tension device 55 of the aforedescribed character extending between each of' the posts 45-47 and the deck 38, compressed air is introduced to the space 68 beneath the roof 11 by a pair of blower units 71 and 72 (see FIGURES 2 and 3). The blower unit 71 (see FIGURE 3) is a relatively large unit connected to a manway hatch 75 in the wall 15 of the tank 10, while the blower unit 72 (see FIGURE 2) is a smaller unit connected to a port 76 in the roof 11.

As air is pumped into the space 68 by the collective efforts of the blower units 71 and 72, it is substantially retained therein by the. sealing arrangement 18 surrounding the roof 11, and the plugs 40 in the corresponding sleeves 36. Of course there is a certain amount of air leakage from around the posts 45-47 as well as from various other places. The blower units 71 and 72 are of sufficient capacity to develop a necessary `pressure of approximately 2.3 ounces per square inch to elevate the roof in question, however. In the present instance the roof 11 weighs approximately one hundred and sixty-five thousand pounds.

The relatively large blower unit 71 is preferably capable of delivering approximately twenty-two hundred feet of air per minute to the space 68 beneath the tank roof 11. The blower unit 71 includes a conventional electric blower 80 driven by a power source (not shown) and joined to an attachment plate 81 by conventional machine bolts (not shown). The attachment plate 81 is, in turn, secured to an annular flange 83 defining the manway 75 in the same manner. The ange 83 is secured in the wall 15 by welding or the like.

On the other hand, the relatively small blower unit 72 is preferably capable of delivering approximately seven hundred and sixty cubic feet of air per minute to the space 68 beneath the roof 11. The smaller blower unit 72 includes a blower driven by a power source (not shown) and connected to a nozzle 91 by an air hose 92. The nozzle 91 is, in turn, suitably mounted on a lianged ring 93 defining the hatch port 76. The anged ring 93 is secured in an appropriate passage through a corresponding pontoon section 27 by welding or the like.

The air pressure developed in the space 68 by the combined efforts of the blower units 71 and 72, approximately 2.3 ounces per square inch, as pointed out, elevates the roof 11 slowly. As the roof 11 rises on this cushion of air it has a natural tendency to tilt as a result of the slight inequalities in weight distribution about the deck 28, for example. In the method embodying features of the present invention, this tendency is overcome and the roof 11 rises evenly.

It is the adjustable tension devices 55 which provide the medium for maintaining the roof in level relationship as it rises on its cushion of air. Personnel atop the roof 11 adjacent the posts 45, 46, 47 manipulate the levers 65 of the clutch units 64 as the roof rises, to take up slack in the cables 60, 61 in the aforedescribed manner and maintain them in substantially taut relationship between the rings 59 on the upper ends 56 of corresponding posts, and the deck 38 adjacent the base of each post. Since the tension devices 55 are spaced at approximately 120 around the periphery of the roof 11, no one side of the roof can dip. Actually, in practice it has been found satisfactory to manipulate the tension devices 55 only when the roof 11 begins to tilt. At such time, construction personnal shut off the small blower unit 72 by closing its inlet nozzle 100 with a port plate 102. The unit 71 continues to supply air at a rate calculated to hold the roof at the level in question. One of the tension devices 55 is then manipulated to raise the corresponding dipping side of the roof 11.

Since utilization of the present method assures that the roof 11 does not tilt as it rises on a cushion of air, wedging action or the like of the roof is prevented. Accordingly, the possibility of damage to the seal arrangement 18 is obviated, for example. Furthermore, the periphery of the roof 11 and the tank wall 15 are not Subjected to excessive stress from any such wedging action. In addition, construction personnel working on the roof 11 as it is elevated have a stable platform and cannot suddenly be upended by the roof 11 tilting olf to one side.

Utilizing the method of the present invention, the roof 11 is raised to a predetermined height in somewhat less than two hours. When the roof 11 has reached this predetermined height, as illustrated in dotted lines at A in FIGURE 2, transverse apertures 105 in the upper end 106 of each sleeve 36 (see FIGURE 4) are in alignment with substantially identical apertures 107 (see FIGURE 3) through corresponding support posts 45-47. Appropriately sized locking pins 108 are then inserted through the aligned apertures 105 and 107; accordingly, the posts 45-47 are secured to corresponding sleeves 46. At this point it should be established that very little working room remains for manipulating the tension devices 55 when the roof approaches position A. Accordingly, it is often found to be desirable to secure extensions (not shown) to the upper ends of the support posts 45-47 and secure the cables 60 to them.

Subsequently, pipe posts 110 are dropped into each of the remaining sleeves 36 in a prescribed order. First the inner concentric ring 34 of the sleeves 36 receives pipe posts 110; then the outer ring 32, and finally the intermediate rings. As each pipe post 110 is pushed through a corresponding sleeve 36, it pushes the seated plug 40 downwardly into the space 68 beneath the roof 11, of course. The corresponding post 110 is immediately lpinned to its sleeve 32 by a pin 10S extending through aligned apertures 105, 107, as hereinbefore discussed.

It should be pointed out at this time that after the roof 11 has been raised to the dotted line position A in FIG- URE 2 and pinned, each post 25-27 is sealed with maskposts; The adjustable tensionk devices 55 are now removed, as well as the small blower unit 72. Construction personnel then may enter the space 68 under the roof 11 through opened manways 75 (there may be a number of them) to complete required work beneath the roof 11.

In yaddition to various seam and tack welding oper-ations hereinbefore referred to, across members 120 are preferably secured to the posts 45-47 and 110 adjacent their lowermost ends 53 to serve as lower limit stops for the floating roof during operation, as seen in FIGURE 2 in the dotted line illustration B of the roof 11 oating on a stored liquid. The cross-members 120 might be pins secured to cor-responding vposts by welding or the like. Their significance and utility Will Ibe better understood .after a description of the tank 10 in operation.

After work beneath the roof 11 is completed, the manways 75 are closed with suitable plates (not shown). The stored products liquid 12 is pumped into the space 68 beneath the roof 11 and rises unrestrained until it reaches the bottom deck 1.16 of the roof 11 supported on the posts 45-47 and 110 in the manner hereinbefore described. As the stored liquid 12 rises, trapped gas is bled through the roof 11 via the hatch port 76 or other ports. When the Ilevel of the stored liquid 12 reaches the roof 11 in its supported relationship, and more liquid is introduced, the roof 11 floats upwardly on the surface of the liquid, of course. Naturally the posts 45-47 and oat upwardly with the rising roof 11, since they are pinned to corresponding sleeves 36 by the pins 108.

When lthe ltank 10 has been suitably -lled with stored liquid 12, and the roof 11 has risen to its dotted line position B illustrated in FIGURE 2, the pins 10-8 are preferably removed from the aligned apertures 105 and 107 through the sleeves 36 and, corresponding posts, making the posts -slidable in the sleeves. They may be left as such or pulled upwardly, as illustrated in dotted lines in FIGURE 3, to where a second aperture 121 through each of the posts 45-47 and 110 appears above the uppe-r end 56 of each sleeve 36. In the latter case, the pins 108 are re-inserted in the apertures 105, 121 and, as well be recognized, the posts 45-47 and 110 are fixed in the sleeves 36 in -a position wherein a relatively short length of pipe extends below the roof 11. This establishes an `alternative bottom stop arrangement during tank 10 operation, as pointed out below.

It will now be seen that as stored liquid 12 is withdrawn from the ta-nk 10 durin-g the normal course of operation, and the roof- 11 sinks Ilower, the base plates 54 on the lower ends 53 of the posts 45-47 and 110 re-engage the bottom 20 of the tank 10. The roof 11 continues to sink lower, in the case where the posts are not pinned to the sleeves 36. When the roof 11 sinks to a position whereupon the sleeves 36, or rather the lower ends 42 of the sleeves 36, engage the limit stop members 120, the roof 11 is supported on the limit stop members 120 and can sink no lower. Accordingly, certain xtures such as drain equipment and the like (not shown) underneath the roof 11 -are not squashed by the weight of the ,roof 11. Where the posts are pinned to sleeves 36 vat the lower apertures121, the lower stop members can be dispensed with of course.

Upto this point, the method embodying features of the present invention has been described in the context of a floating roof 11 employing va 4seal arrangement 18 of the foam type, as disclosed in the aforementioned Bodley application entitled, Seal However, the method is equally adaptable to utilization with oating roofs 11 employing standard shoe type seal, also, of course, or to other seal arrangements.

Referring to FIGURE -6, for example, a shoe type seal is shown mounted on the peripheral wall 17 of the floating roof 11, the shoe type seal 130 being modified to suit the method embodyin-g features of the present invention. The seal 130 includes an annular fabric seal element 131 secured to the upper edge of the peripheral wall 17 of the roof 11 by a series of suitable clarnps 132.

The outer periphery 135 of the seal element 131 is secured to a series of galvanized shoes 136 which normally slide on the tank wall 15, urged by appropriate resilient means (not shown) extending between the U-clamps 137 and the periphery of the roof 11 in the vicinity of the clamps 132.

In order to provide the good air seal necessary for use with the method embodying the features of the present method, polyurethane foam sections 140 are placed between the tops of the galvanized shoes 136 and bolted through the shoes 136 to the U-clarnps 137 with machine bolts 138 normally used for securing the shoes 136V to the U-clamps 137. In order to prevent the bolts 138 from pulling through the foam 140, wooden laths 141 are used to function as a washer and also to produce clamping of the foam between the bolts. Butchers wax paper 142 is als-o preferably inserted between the foam 140 and the shell 15 in order to minimize friction. Wooden wedges 145 are inserted between the clamps 132 on the rim of the roof 11 and the U-clamps 137 on the shoes 136. Also, heavy grease is preferably spread on the wall 15 just above the :shoes 136. The foregoing provides an excellent air sealing arrangement, of course.

Regardless of the type of sealing arrangement used around the periphery of the roof 11, of course, it is only necessary that a satisfactory seal against the excessive loss of air be provided. It will thus be understood that a variety of seal arrangement might be used within the scope of the present invention.

It will now be recognized that a new improved method of constructing `a floating roof storage tank and, more particularly, of elevating the roof 11 in a floating roof storage tank 10, has been shown and described. This method facilitates elevating the tank roof 11 simply and expeditiously, with a minimum of labor and cost, while assuring that the seal arrangement (18 for example), lthe tank roof 11, and tank wall are not damaged. Furthermore, dangers to construction personnel are substantially eliminated.

While the embodiment described herein is at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modiiications and improvements as fall within the true spirit and scope of the invention.

What is desired to be claimed and Secured by Letters Patent of the United States is:

1. A method of constructing a floating roof in a storage tank, comprising the steps of; assembling the tank roof on the tank bottom within the tank shell, passing a predetermined number of support posts through the roof in a predetermined pattern to rest on the tank bottom, providing adjustable tension means between the tank roof and said predetermined posts above the tank roof, introducing gas under pressure beneath the roof to elevate it slowly, adjusting said tension means as the roof is elevated to maintain it in substantially level relationship, and securing the roof to said support posts at a prescribed elevated position whereby said roof is prevented from descending below a desired position when iiuid is removed from the tank.

2. The method of claim 1 further characterized in that said adjustable tension means includes first exible means secured to said roof, second flexible means secured to said predetermined posts above said roof, and take-up clut-ch means interconnecting said flexible means.

3. A method of constructing `a floating roof in a storage tank, comprising the steps of; assembling the tank roof on the tank bottom within the tank shell, provi-ding a predetermined number of sleeve means in said roof `arranged in a predetermined pattern around its periphery, sliding a support post downwardly through each of said predetermined sleeve means to rest on the tank bottom, providing adjustable tension means between the tank roof and said predetermined posts above the tank roof, introducing gas under pressure beneath the roof to elevate it slowly, adjusting lsaid tension means as the roof is elevated to maintain it in substantially level relationship, and securing the roof to said support posts at a prescribed elevated position whereby said roof is prevented from descending below a desired position when iiuid is removed from the tank.

4. The method of claim 3 further characterized by and including the step of establishing a relatively gas tight seal between the periphery of the tank roof and the tank Wall precedent to introducing gas under pressure beneath the roof.

5. The method of claim 3 further characterized in that said predetermined number of sleeve means arranged in a predetermined pattern comprise three sleeve means spaced angularly approximately `apart around the periphery ofthe tank roof.

6. A method of constructing a oating roof in a storage tank, comprising the steps of; assembling the tank roof on the tank bottom within the tank wall, providing a relatively gas tight seal between the periphery of the tank roof and the tank wall, providing a large plurality of sleeve means in said sleeve means, sliding a support post downwardly through each of a predetermined number of sleeve means arranged in a predetermined pattern around the periphery of the roof whereby said support posts come to rest on the tank bottom, providing adjustable tension means between the upper ends of said support posts and the roof adjacent said predetermined sleeve means, introducing gas under pressure beneath the roof to elevate it slowly, adjusting said tension means as the roof is elevated to maintain it in substantially level relationship, and securing the roof to said support posts at a prescribed elevated position whereby said roof is prevented from descending below a desired position when fluid is removed from the tank.

'7. The method of claim 6 further characterized by and including the additional step of sliding support posts downwardly through each of the remaining sleeve means when the roof has been raised to a predetermined height on a cushion of gas, and securing the roof to each of said support posts at said predetermined height.

8. The method of claim 7 further characterized in that said sleeve means are ysealed olf by providing plugs in their lower ends, the introduction of support posts into corresponding sleeves causing said sleeves to be forced out of said lower ends.

9. The method of claim 7 further characterized in that said predetermined number of sleeve means arranged in a predetermined pattern comprises three sleeve means angularly displaced approximately 120 around the periphery of the roof.

10. A method of constructing a roof in a storage tank having a bottom, an annular wall extending upwardly from said bottom, and a roof, comprising the steps of: constructing said roof upon said bottom and within said wall, maintaining a clearance between said wall and the circumference of said rooi:` whereby said roof is vertically movable within said wall, providing sealing means in said clearance to farm a movable uid seal between said -roof and said wall, providing structure secured to the (References on following page) Q References Cited by the Examiner 2,847,755 UNITED STATES PATENTS g 7/1946 Laird 22o-26 3,033,411 6/ 1950 Perkins 29-429 5 5/1951 Allen 29-431 12/1953 Cord et a1.

l() Mummert et al. 29-429 Hanna 29-469 X Lee 220-26 X Brucker et al. 220-18 CHARLIE T. MOON, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 ,319,329 May 16, 1967 Herbert K. Knutsen et al.

It is hereby certified that error appears n the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 2, lines 33 and 40, and column 5, lines 40, 5() and 65 for "A", each occurrence, read "A" column 3, lines 33 and 41 for "room", each occurrence, read roof line 62, for "on" read of column 5, line 21, for "personnal" read personnel column 6, line 7, for "across-members" read crossmembers lines ll and 32, for "B", each occurrence, read "B" column 8, line 6l, for "farm" read form Signed and sealed this 28th day of November 1967.

(SEAL) Attest: Edward M. Fletcher, Ir. EDWARD I, BRENNER Attestng Officer Commissioner of Patents 

10. A METHOD OF CONSTRUCTING A ROOF IN A STORAGE TANK HAVING A BOTTOM, AN ANNULAR WALL EXTENDING UPWARDLY FROM SAID BOTTOM, AND A ROOF, COMPRISING THE STEPS OF: CONSTRUCTING SAID ROOF UPON SAID BOTTOM AND WITHIN SAID WALL, MAINTAINING A CLEARANCE BETWEEN SAID WALL AND THE CIRCUMFERENCE OF SAID ROOF WHEREBY SAID ROOF IS VERTICALLY MOVABLE WITHIN SAID WALL, PROVIDING SEALING MEANS IN SAID CLEARANCE TO FARM A MOVABLE FLUID SEAL BETWEEN SAID ROOF AND SAID WALL, PROVIDING STRUCTURE SECURED TO THE BOTTOM OF SAID TANK AND EXTENDING ABOVE SAID ROOF, PROVIDING CABLE MEANS RELATIVELY MOVABLY CONNECTED TO SAID ROOF AND EXTENDING UPWARDLY THEREFROM INTO FIXED CONNECTION WITH SAID STRUCTURE, INTRODUCING FLUID UNDER PRESSURE BETWEEN THE UNDERSIDE OF SAID ROOF AND SAID BOTTOM TO RAISE SAID ROOF TO A PREDETERMINED ELEVATION, MAINTAINING SAID ROOF IN HORIZONTALLY LEVEL RELATIONSHIP WITH SAID CABLE MEANS AS SAID ROOF IS RAISED, AND SECURING SAID ROOF TO SAID STRUCTURE AT A PRESCRIBED ELEVATED POSITION WHEREBY SAID ROOF IS PREVENTED FROM DESCENDING BELOW A DESIRED POSITION WHEN FLUID IS REMOVED FROM THE TANK. 